In recent years, there are demands for reducing thicknesses, sizes, weights, etc. of electronic devices such as IC cards and mobile phones. In order to meet the demands, semiconductor chips which are to be integrated into these electronic devices must be thin. A current semiconductor wafer, which constitutes a base of a semiconductor chip, has a thickness (film thickness) within a range from 125 μm to 150 μm; however, for a next-generation chip, it is said that a semiconductor wafer must have a film thickness within a range from 25 μm to 50 μm. In order to obtain a semiconductor wafer whose film thickness is within this range, a step for thinning a semiconductor wafer is indispensable. The step for thinning the semiconductor wafer is carried out, for example, as follows (see Patent Literature 1):
First, via a tape whose both sides have adhesive layers or an adhesive, a support plate for protecting a semiconductor wafer is bonded to the semiconductor wafer such that the support plate covers a circuit-formed surface of the semiconductor wafer. Next, the semiconductor wafer is turned over, and a back surface of the semiconductor wafer is ground by a grinder, so that the semiconductor wafer is thinned. Subsequently, the back surface of the thinned semiconductor wafer is fixed onto a dicing tape which is supported by a dicing frame. Then, in this state, the support plate, which covers the circuit-formed surface of the semiconductor wafer, is stripped off. Thereafter, the semiconductor wafer is divided into chips by a dicing device.
However, carrying out the thinning step in the above manner causes the adhesive and/or the like to remain on the circuit-formed surface of the semiconductor wafer after the support plate is stripped off. Therefore, the adhesive and/or the like stuck thereon must be removed in order to clean the circuit-formed surface of the semiconductor wafer. Namely, after the support plate covering the circuit-formed surface of the semiconductor wafer is stripped off and before the semiconductor wafer is divided into chips by the dicing device, the surface of the semiconductor wafer needs to be subjected to a cleaning process in the state where the semiconductor wafer is fixed onto the dicing tape.
However, since the dicing tape has a surface area greater than that of the semiconductor wafer, an exposed surface of the dicing tape is located along the outer periphery of the semiconductor wafer. Therefore, with a generally-used cleaning process method such as (i) supplying a processing liquid while rotating the semiconductor wafer or (ii) immersing the semiconductor wafer into a processing liquid, the processing liquid processes not only the surface of the semiconductor wafer but also the exposed surface of the dicing tape. Further, depending on the type of the processing liquid used in this process, the dicing tape may be deteriorated.
In order to address this, there have been developed some techniques for preventing the outer peripheral part (e.g., the exposed surface of the dicing tape) of the process-target surface (i.e., the surface to be processed) from being processed by the processing liquid which is used to process the process-target surface (see Patent Literatures 2 and 3).
Patent Literature 2 describes a technique for storing a processing liquid in a processing jig mounted onto a process-target surface, in order to process only the process-target surface by the processing liquid.
Patent Literature 3 describes a technique for supplying a first processing liquid to a substantial boundary between a process-target surface and its outer peripheral part while supplying a second processing liquid to the process-target surface, so that the outer peripheral part is protected from the second processing liquid by the first processing liquid, in order to process the process-target surface by the second processing liquid while preventing the outer peripheral part from being processed by the second processing liquid, which is used to process the process-target surface.